Arbitration service CISAS has decided that T-Mobile's use of precognition in setting prices was cheating - allowing some customers to escape thir contracts - though in other cases CISAS has decided just the opposite.

The facts are that the mobile operator pushed up prices by 3.3 per cent, informing customers that this was within the government's Retail Price Increase and therefore allowed under their contracts. But when the letter was written, the RPI was only 3.2 per cent. T-Mobile guessed it would go up and that caused some punters to jump. It turns out the guess was accurate, but that's not good enough for CISAS, which has ruled that at least one customer is entitled to shrug off the contract.

CISAS is one of two UK arbitration bodies set up to deal with customer complaints. Communication providers are required to sign up to at least one of the schemes, which kick in only when the operator's own complaints procedure has reached deadlock, as it had in this case.

One unnamed customer posted the ruling onto a forum at Moneysaving Expert where malcontents have been gathering to marshal efforts against T-Mobile and its owner EE. The ruling clearly states that "neither party could have been aware of the RPI figure for March 2013 at the time the notice was given". So it is rather suprising that other complaints have been rejected by CISAS.

The arbitrator claims that every case is evaluated on its own merits, but given that so many people experienced the same thing one might imagine the same result would apply. Forum posters are now in deep discussions about what swayed the judgements and which particular adjucators are ruling which way, in the hope of finding patterns to help others.

T-Mobile was initially dismissive of complaints, claiming that it was confident the RPI would increase to 3.3 per cent and everything was legit as the new pricing wouldn't apply until after that happened. We've tried repeatedly to contact T-Mobile, since the CISAS ruling was published, but so far we've had no official response. ®